title: Primary and secondary kinase genotypes correlate with the biological and clinical activity of sunitinib in imatinib-resistant gastrointestinal stromal tumor.
abstract: OBJECTIVE
  Most gastrointestinal stromal tumors (GISTs) harbor mutant KIT or platelet-derived growth factor receptor alpha (PDGFRA) kinases, which are imatinib targets. Sunitinib, which targets KIT, PDGFRs, and several other kinases, has demonstrated efficacy in patients with GIST after they experience imatinib failure. We evaluated the impact of primary and secondary kinase genotype on sunitinib activity.
  
  
  METHODS
  Tumor responses were assessed radiologically in a phase I/II trial of sunitinib in 97 patients with metastatic, imatinib-resistant/intolerant GIST. KIT/PDGFRA mutational status was determined for 78 patients by using tumor specimens obtained before and after prior imatinib therapy. Kinase mutants were biochemically profiled for sunitinib and imatinib sensitivity.
  
  
  RESULTS
  Clinical benefit (partial response or stable disease for > or = 6 months) with sunitinib was observed for the three most common primary GIST genotypes: KIT exon 9 (58%), KIT exon 11 (34%), and wild-type KIT/PDGFRA (56%). Progression-free survival (PFS) was significantly longer for patients with primary KIT exon 9 mutations (P = .0005) or with a wild-type genotype (P = .0356) than for those with KIT exon 11 mutations. The same pattern was observed for overall survival (OS). PFS and OS were longer for patients with secondary KIT exon 13 or 14 mutations (which involve the KIT-adenosine triphosphate binding pocket) than for those with exon 17 or 18 mutations (which involve the KIT activation loop). Biochemical profiling studies confirmed the clinical results.
  
  
  CONCLUSIONS
  The clinical activity of sunitinib after imatinib failure is significantly influenced by both primary and secondary mutations in the predominant pathogenic kinases, which has implications for optimization of the treatment of patients with GIST.
authors.affiliation: Division of Hematology/Oncology, Department of Medicine and Cell and Developmental Biology, Portland Veterans Affairs Medical Center and Oregon Health and Science University Cancer Institute, Portland, OR 97239, USA. Heinrich@ohsu.edu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Heinrich
authors.forename: Robert G
authors.initials: RG
authors.lastname: Maki
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Corless
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Antonescu
authors.forename: Amy
authors.initials: A
authors.lastname: Harlow
authors.forename: Diana
authors.initials: D
authors.lastname: Griffith
authors.forename: Ajia
authors.initials: A
authors.lastname: Town
authors.forename: Arin
authors.initials: A
authors.lastname: McKinley
authors.forename: Wen-Bin
authors.initials: WB
authors.lastname: Ou
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Fletcher
authors.forename: Christopher D M
authors.initials: CD
authors.lastname: Fletcher
authors.forename: Xin
authors.initials: X
authors.lastname: Huang
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Cohen
authors.forename: Charles M
authors.initials: CM
authors.lastname: Baum
authors.forename: George D
authors.initials: GD
authors.lastname: Demetri
mesh_terms: D000328:Adult; D000368:Aged; D001549:Benzamides; D018450:Disease Progression; D018572:Disease-Free Survival; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005091:Exons / Q000235:genetics; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D005838:Genotype; D006801:Humans; D000068877:Imatinib Mesylate; D007211:Indoles / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010766:Phosphorylation; D010879:Piperazines / Q000627:therapeutic use*; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D011743:Pyrimidines / Q000627:therapeutic use*; D011758:Pyrroles / Q000627:therapeutic use*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000077210:Sunitinib
chemical_list: D001549:Benzamides; D007211:Indoles; D010879:Piperazines; D011743:Pyrimidines; D011758:Pyrroles; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha; D000077210:Sunitinib